boards: hifive1: remove incorrect alias for GPIO use of LEDs

[pabigot]

The devicetree for this board only provides PWM-compatible LEDs. Remove the aliases that suggest it supports GPIO-compatible LEDs.

Fixes #30315 by producing:

/mnt/nordic/zp/zephyr/samples/basic/blinky/src/main.c:24:2: error: #error "Unsupported board: led0 devicetree alias is not defined"
   24 | #error "Unsupported board: led0 devicetree alias is not defined"
      |  ^~~~~

[nashif]

@pabigot you have this board and able to flash it?

[pabigot]

@pabigot you have this board and able to flash it?

@nashif No; I have the hifive1_revb but this is an earlier version. The devicetree clearly fails to define GPIOs for the LEDs, so I think removing the aliases is the right solution. This causes the build to fail just as it does on an ESP32 board that also has no LEDs.

#30315 (comment) confirms that the PWM LED example worked on this board, so all should be as expected after removing the invalid aliases.

[nashif]

@nashif No; I have the hifive1_revb but this is an earlier version.

yeah, same here, I am thinking we should just drop this board. It requires tools and openocd that we do not have or support.